In an EEPROM, the logical value of a bit stored in a memory point may be represented by a threshold voltage of a floating-gate transistor, which may be modified by writing or erase operations. Writing or erasing may be carried out on a floating-gate transistor by injecting electrical charges into the transistor gate, or removing them from it, by a tunnel effect (the Fowler-Nordheim effect), using a high programming voltage Vpp which may be about 10 to 20 volts, and is typically 16 volts.
This high voltage of 16 volts, which is generally required for programming EEPROMs, may not be reduced and may set considerable constraints on the processing and reliability of the product. This is because the lithographic reduction, i.e. the increase of the etching resolution, tends to decrease the operating voltages. This high programming voltage may become more problematic, particularly in relation to the punchthrough and leakage of the source/drain junctions of the transistors and the breakdown of the gate oxides. These risks of breakdown and premature aging of the transistors may have a direct impact on the reliability of the product.